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 * @Date: 2022-12-22 11:51:20
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<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        // var num = null;
        // console.log(num);
        // console.log(typeof num);

        // var res = String(num);
        // console.log(res);
        // console.log(typeof res);


        // var num = 0xabc;
        // console.log(num);
        // console.log(typeof num);

        // var res = num.toString();
        // console.log(res);
        // console.log(typeof res);

        // console.log(1+2+3+6);
        // console.log(1+'2'+3+6);// 1236
        console.log(1+'2'-3+6);
        // 1   字符串12
        // 12 - 3 9
        // 9 + 6 = > 15
        

    </script>
</body>
</html>